Suspicious Car Troubles

Pooteewheet's car has been running a little rough, so we took it in to have it looked at. Our favorite fixit guy closed up shop when Eagan eminent domained him, so we took it to the local BP where one of the mechanics had gone. Summary:

• Hooked it up to a machine for an hour and a half and found nothing. Note, they never took it for a road test which is what our old mechanic always did. We're not imagining that it's running rougher than it did. Maybe it's just a matter of waiting until something breaks.
  
• They left it in the lot with the parking break off and the parking lights on.
• When Pooteewheet drove the car off, it wasn't just that the parking lights were on, all the lights were on, but the low beams, which had been fine when she brought it in, were burnt out. Both of them.

They've offered to replace them, but is there a way to hook up the diagnostic wrong such that it burns out your bulbs? And if you live in the Eagan area, where do you take your car? We're looking for a new mechanic. This one won't do.